It will be appreciated that there are numerous applications in industry in which valve sealing arrangements are required to control the flow of a fluid passing through a valve. One example of an application is in safety valves which are used to control the pressure of a fluid in a closed system. In this application a sealing arrangement is required which can form a completely leak proof seal when the valve is held closed during normal operation conditions and can break the seal to allow fluid to pass through the valve when the valve is opened in the event that the pressure in the system rises above threshold level. Such sealing arrangements typically provide a valve disk (or plunger) with a sealing member fitted in a groove machined around the circumference of the valve disk. The valve disk is then forced against a valve seat which closes the flow path preventing the flow of fluid through the valve. Such an arrangement is well suited to the use of a highly flexible elastomer seal. The seal can be stretched over the valve disk and slipped into the machined groove which holds it in place. In applications where a valve may be used with a wide range of industrial liquids such as with hot water, saturated steam or hot gases, elastomer seals do not perform as well as tougher but less flexible seals such as PTFE seals. A problem with using less flexible seals is that the quality of the seal is more dependent on accurate alignment between the disk and the seat.